Pain Receptors And Stimuli Psychology Essay

Pain is an unpleasant feeling that is transferred to the brain by sensory neurons. The discomfort signals actual or potential damage to the body. However, pain is more than a sensation, or the physical consciousness of pain; it also includes perception, the subjective illustration of the discomfort. Perception gives information on the pain’s location, intensity, and something about its nature. The different conscious and unconscious responses to these sensation and perception, including the emotional response, add additional definition to the entire concept of pain.

Pain Receptors and Stimuli All receptors for pain stimuli are free nerve endings of groups of myelinated or unmyelinated neural fibers plenty distributed in the superficial layers of the skin and in certain deeper tissues such as the periosteum, surfaces of the joints, arterial walls, and the falx and tentorium of the cranial cavity. The delivery of pain receptors in the gastrointestinal mucosa apparently is similar to that in the skin; thus, the mucosa is quite sensitive to irritation and other painful stimuli. Although the parenchyma of the liver and the alveoli of the lungs are almost entirely insensitive to pain, the liver and bile ducts are extremely sensitive, as are the bronchi and parietal pleura. [1]

Some pain receptors are selective in their response to stimuli, though most are sensible to more than one of the following matters of excitation: 1 mechanical stress of trauma; 2 most of heat and cold; and 3 chemical substances, such as histamine, prostaglandins, bradykinin, and acetylcholine. Pain receptors, unlike other sensory receptors in the body, don’t adjust or become less sensitive to repeated stimulation. Under certain clauses the receptors become more sensitive over a period of time. This accounts for the fact that as long as a traumatic stimulus persists the man will carry on being aware that damage to the tissues is occurring.

The body is able to identify tissue damage because when cells are wasted they release the chemical substances previously mentioned. These substances can stimulate pain receptors or cause straight damage to the nerve endings themselves. A lack of oxygen supply to the tissues can also create pain by causing the release of chemicals from ischemic tissue. Muscle spasm is another cause of pain, presumably because it has the indirect result of causing ischemia and stimulation of chemosensitive pain receptors.

TRANSMISSION AND RECOGNITION OF PAIN When superficial pain receptors are excited the impulses are convey from these surface receptors to synapses in the dorsal horns of the spinal cord. They then move upward along the sensory pathways to the thalamus, which is the primary sensory relay station of the brain. The dorsomedial nucleus of the thalamus bulge to the prefrontal cortex of the brain. The sober perception of pain presumably takes place in the thalamus and lower centers; interpretation of the character of pain is presumably the role of the cerebral cortex.

The perception of pain by an individual is very complex and individualized. The cerebral cortex is concerned with the assessment of pain and its type, intensity place, and thus, an intact sensory cortex is necessary to the perception of pain. In addition to neural effect that transmits and modulates sensory input, the perception of pain is influenced by psychological and cultural responses to pain-related stimuli. A man can be unaware of pain at the time of a sharp injury or other very stressful situation or when experiencing an emotional emergency. Cultural influences also precondition the perception of and response to painful stimuli. The retroaction to similar circumstances can size from complete stoicism to histrionic behavior. [2]

Pain Control There are various theories related to the physiologic control of pain but none has been entirely verified. The gate control theory, which proposed that pain impulses were, mediated in the substantia gelatinosa of the spinal cord with the dorsal horns working as “gates” that managemented entry of pain signals into the central pain pathways. Pain signals would compete with tactile signals with the two continuously balanced against each other.

As this theory was first proposed, researchers have understanded that the neuronal circuitry it hypothesizes is not exactly correct. Even so, there are internal systems that are now known to happen naturally in the body for controlling and mediating pain. One such system, the opioid system, involves the generation of morphinelike substances called enkephalins and endorphins. These two are naturally happening analgesics found in various parts of the brain and spinal cord that are concerned with pain perception and the transmission of pain signals. Signals begin from stimulation of neurons in the gray matter of the brain stem travel nethermost to the dorsal horns of the spinal cord where incoming pain impulses from the periphery terminate. The descending signals block or significantly diminish the transmission of pain signals up to along the spinal cord to the brain where pain is perceived by releasing these substances.

In addition to the brain’s opioid system for ruling the transmission of pain impulses along the spinal cord, there is another action for the control of pain. The stimulation of large sensory fibers prolonged from the tactile receptors in the skin can suppress the transmission of pain signals from thinner nerve fibers. It is as if the nerve pathways to the brain can accommodate only one type of signal at a time, and when two kinds of impulses simultaneously come at the dorsal horns, the tactile sensation accepts precedence over the sensation of pain.

The detection of endorphins and the impediment of pain transmission by tactile signals has supplied a scientific illustration for the effectiveness of similar techniques as relaxation, massage, application of liniments, and acupuncture in the manage of pain and discomfort.

Pathophysiology & Clinical Implications


Pain has a biologically significant protective function. The sensation of pain is a usual reply to injury or disease and is a result of normal physiological processes within the nociceptive system, with its complex of stages previously described. There may also be another manifestations of pain related to tissue injury containing hyperalgesia, an exaggerated response to a noxious stimulus, the perception of pain from normally innocuous stimuli. Hyperalgesia and allodynia are the effect of changes in either the peripheral or CNS, referred to as peripheral or central sensitization, respectively.

Genetic and environmental factors help to sensitization resulting in persistent pain in some individuals even after healing has taken place. Nociceptors not only signal sharp pain, but when chronically sensitized, contribute to persistent pathological pain disorders disarray from previous injury or ongoing affection. Chronic pain is also marked by the abnormal state and function of the spinal cord neurons which become hyperactive. This hyperactivity is the result of transmitter release by spontaneously active primary afferent neurons and a raised responsiveness of postsynaptic receptors .A hyperexcitable state of synaptic transmission at the back horn is further kept up by release of biologically active factors from activated glia. The condition of hyperexcitability is aggravated by the loss of inhibitory interneurons involved in the adjustment of pain.

Under normal situation the nociceptive sensory system returns to a, usual functional state as soon as healing takes place. But many characterize of sensitization persist and are manifest as chronic pain and hyperalgesia, particularly when the nervous system itself is injured initial to chronic neuropathic pain. Imaging studies have shown that chronic pain is gone with by permanent structural variation in specific brain areas that play a crucial role in nociception.


Acute Pain

Acute pain starts suddenly and is normally sharp in quality. It works as a warning of disease or a threat to the body. Acute pain may be performed by many events or circumstances, such as Surgery

1 Broken bones 2Burns or cuts

3 Dental work 4Labor and childbirth

Acute pain may be middle and last just a moment, or it may be acute and last for months. In most cases, acute pain doesn’t last longer than seven months and it vanishes when the underlying cause of pain has been treated or has healed. Unrelieved acute pain, though, may lead to chronic pain.

Chronic Pain

Chronic pain continues despite the fact that an injury has healed. Pain signals active in the nervous system for weeks, years, or months, Physical effects include tense muscles, restricted mobility, and changes in appetite. Emotional effects comprehend depression, anger, and fear of re-injury. Such a fear may hinder a person’s skill to return to normal work or leisure activities. Common chronic pain complaints comprise [3]

Headache Psychogenic pain

Low back pain

Cancer pain

Arthritis pain

Neurogenic pain

Chronic pain may have arisen with an initial trauma, infection or, injury there may be an ongoing cause of pain. Some people bear chronic pain in the absence of any past injury of body damage.

CLASSIFYING PAIN Pain is generally divided according to its location, frequency, duration, underlying cause, and intensity. Classification of pain is thus intricate and can be a source of confusion for many clinicians. Many practitioners now universally use several various classification systems. Clear distinctions between these systems are not always possible. the more simplistic the classification of pain, the greater the number of omissions and overlaps that can happen.4 To successfully manage pain, practitioners must be able to work with pain classifications that encompass all considerations and be able to switch from model to model, depending on a patient’s individual circumstances.[4]

Classification of pain classifying pain is helpful to guide assessment and treatment. There are many ways to classify pain and classifications may overlap. The usual types of pain include:

Nociceptive represents the normal response to noxious insult or injury of tissues such as skin, muscles, visceral organs, joints, tendons, or bones.

Examples include: Visceral hollow organs and smooth muscle; usually referred Somatic musculoskeletal cutaneous, often well localized

Neuropathic pain begun or reasoned by a primary lesion or disease in the somatosensory nervous system.

Sensory abnormalities range from defects perceived as numbness to paresthesias and to hypersensitivity such as tingling. Examples include, but are not limited to, diabetic neuropathy, postherpetic neuralgia, spinal cord injury pain, and post-stroke central pain. [5]

Inflammatory An effect of activation and sensitization of the nociceptive pain pathway by a variety of mediator’s exemption at a site of tissue inflammation.

The mediators that have been implicated as key players are proinflammatory cytokines such IL-1-beta, IL-1-alpha, IL-6 and TNF-alpha, reactive oxygen species, chemokines, lipids, acid, vasoactive amines ATP, and other factors exemption by infiltrating leukocytes, vascular endothelial cells, or tissue resident mast cells

Examples include appendicitis, inflammatory bowel disease, rheumatoid arthritis, and herpes zoster.

Clinical Implications of classification Pathological processes never happen in isolation and consequently more than one mechanism may be present and more than one type of pain may be detected in a single patient; for example, it is known that inflammatory mechanisms are involved in neuropathic pain.

There are well-recognized pain disorders that aren’t easily classifiable. Our understanding of their underlying actions is still inchoate though specific therapies for those disorders are well known; they include migraine, cancer pain, and other primary headaches and wide-spread pain of the fibromyalgia type.

Pain Intensity can be broadly categorized as: mild, moderate and severe. It is common to use a numeric scale to rate pain intensity where 0 = no pain and 10 is the worst pain imaginable:

Severe >8/10

Mild <4/10

Moderate 5/10 to 7/10

Time course Pain duration

Acute pain pain of less than 2 to 6 months duration [6]

Chronic pain pain lasting for more than 3-7 months, or persisting beyond the course of an acute disease, or after tissue healing is finish.

Acute-on-chronic pain acute pain flare superimposed on underlying chronic pain.

Managing pain

Considering the various reason and model of pain, like wise its nature and intensity, management can ask an interdisciplinary approach. The elements of this access include treating the underlying cause of pain, nonpharmacological and pharmacological therapies, and some invasive procedures.

Cognisance the cause of pain underpins the idea of managing it. Injuries are renovation, diseases are diagnosed, and certain encounters with pain can be expected and treated prophylactically in any event, there is no endorsement of urgent relief from pain. Cure can be impeded by pain and quality of life can be damaged. Hence, pharmacological and other therapies have developed over time to address this part of disease and injury.

PHARMACOLOGICAL OPTIONS Pain-relieving drugs, otherwise called analgesics, include nonsteroidal anti-inflammatory drugs acetaminophen, antidepressants, narcotics, anticonvulsants, and others. Acetaminophen and NSAIDs are available as over-the-counter and prescription treatments, and are frequently the initial pharmacological treatment for pain. This medication can also be used as affiliated to the other drug therapies, which might want a doctor’s prescription.

NSAIDs include ibuprofen aspirin, naproxen sodium and ketoprofen .These drugs are used to cure pain from inflammation and work by blocking manufacturing of pain-enhancing neurotransmitters, such as prostaglandins. Acetaminophen is also active against pain, but its capability to reduce inflammation is limited.

Narcotics may be ineffective against some kind of chronic pain, particularly since changes in the spinal cord may alter the normal pain signaling pathways. In such case, pain can be controled with the help of with antidepressants and anticonvulsants, which are also only available with a doctor’s prescription.

However antidepressant drugs were developed to treat abasement, it has been discovered that they are also active in combating some chronic headaches, pain associated with nerve damage and cancer pain. Antidepressants that have been shown to have analgesic properties include amitriptyline; trazodone and imipramine Anticonvulsant drugs share a same background with antidepressants. Developed to treat epilepsy, certain anticonvulsants were found to alleviate pain as well. Drugs such as phenytoin and carbamazepine are prescribed to treat the pain associated with nerve damage.

Other prescription drugs are used to treat specific kind of pain or specific pain syndromes. For example, corticosteroids are active against pain caused by inflammation and swelling, and sumatriptan was gowned to treat migraine headaches.

Drug administration subsists on the drug kind and the required dose. Some drugs aren’t engaged very well from the stomach and should be injected or administered intravenously. Intravenous jurisdiction and Injections can also be used when top doses are needed or if an individual is nauseous. Following surgery and other medical order, man may have the option of controlling the pain medication themselves. By pressing a button, they can discharge a set dose of medication into an intravenous solution. This procedure has also been employed in other stage requiring pain management. Another mode of administration involves implanted catheters that release pain medication directly to the spinal cord. Delivering drugs in this way can decrease side effects and multiply the effectiveness of the drug. [7]

NONPHARMACOLOGICAL OPTIONS Pain hospitality options that don’t use drugs are every now and then used as adjuncts to, rather than replacements for, drug therapy. One of the betterment of non-drug therapies is that an individual can take a more active stance versus pain. Relaxation techniques, such as meditation and yoga, are used to lower muscle tension and abate stress. Tension and stress may also be reduced among biofeedback, in which an individual knowingly attempts to modify skin temperature, blood pressure, muscle tension, and heart rate.

Participating in concordial activities and exercising can also help rule pain levels. Through, an individual learns beneficial exercises for reducing stress, physical therapy and staying fit. Regular exercise has been linked to produce of endorphins, the body’s natural pain killers.

Acupuncture combines the insertion of small needles into the skin at key points. Acupressure uses these same key points, nevertheless involves applying pressure rather than inserting needles. Both of these systems may work by enticement the body to discharge endorphins. Applying heat or start massaged are very relaxing and help diminish stress. Transcutaneous electrical nerve stimulation applies a little electric current to any parts of nerves, potentially interrupting pain signals and inducing emission of endorphins. To be active, use of TENS should be medically supervised. [8]

INVASIVE PROCEDURES There are several types of invasive procedures that might be used to handle or treat pain: augmentative, anatomic, and ablative. These procedures connect surgery, and certain guidelines should be followed before carrying out a procedure with permanent repercussions. First, the cause of the pain must be clearly identified. Second, surgery should be done only if noninvasive procedures are ineffective. Next, any psychological issues should be addressed. Last, there should be a reasonable expectation of success.

Anatomic procedures combine correcting the injury or removing the factor of pain. Relatively usual anatomic procedures are decompression surgeries, like repairing a herniated disk in the relieving the nerve pressure related to carpal tunnel syndrome. Other anatomic procedure is neurolysis, which involves destroying a portion of a peripheral nerve.

Augmentative cause of action includes electrical stimulation or straight application of drugs to the nerves that are carrying the pain signals. Electrical excitation works on the likewise principle as TENS. In this way, on behalf of applying the present across the skin, electrodes are imprinted to nerves in the spinal cord or stimulate peripheral nerves. Augmentative cause of action also takes in implanted drug-delivery systems. In these systems, catheters are implanted in the spine to grant direct delivery of drugs to the CNS.

Ablative causes of action are expanded by severing a nerve and disconnecting it from the CNS. Though, this system may not address possible modifications within the spinal cord. These shifts perpetuate pain messages and don’t cease even when the link between the sensory nerve and the CNS is severed. With growing understanding of neuropathic pain and improvement of less invasive procedures, ablative causes of action are used less frequently. Although, they do have applications in elect cases of cancer pain, peripheral neuropathy, and other disorders.

PREPARATION Prior to starting management, pain is wholesale evaluated. Pain scales or questionaries’ list are used to join an objective measure to a subjective experience. Objective measurements let health care workers a better understanding of the pain being accustomed by the patient. Evaluation also comprises physical observations and diagnostic tests to determine underlying matters. Certain evaluations necessitate assessments from several including neurology, viewpoints, psychology, psychiatry and physical therapy. If pain is due to a medical policy, management consists of anticipating the kind and intensity of associated pain and managing it preemptively. [9]


Owing to toxicity over the long term, certain drugs can only be used for acute pain or like adjuncts in chronic pain management. NSAIDs have the well-known side effect of causing gastrointestinal bleeding, and long-term utility of acetaminophen has been linked to kidney and liver destruction. Other drugs, especially narcotics have serious side effects, like drowsiness, constipation, and nausea. Serious side effects can also accompany mood swings, confusion, pharmacological therapies; cataract formation, bone thinning, increased blood pressure, and other damage may discourage or impede use of some

Nonpharmacological therapies bear little or no risk. At all events, it is advised that individuals recovering from serious injury consult with their health care supplier or physical therapists before making use of adjunct therapies. Invasive procedures carry uncertainty such to other iatrogenic injury, such as infection, reaction to anesthesia, surgical procedures, and failure.

A hereditary concern about narcotics use has been the uncertainty promoting addiction. Like set in functions to accommodate to its presence. Hence, to elicit the same level of action, it is needy to increase dosage over time. As dosage increases, an individual may set in physically dependent on narcotic drugs.

Although, physical dependence is various from psychological addiction. Physical dependence is characterized by inconvenience if drug administration suddenly stops, while psychological addiction described Psychological addiction is a very certain and needy concern in some facts, but it shouldn’t interfere with a genuine need for narcotic pain relief. Although, caution must be taken with people with a history of addictive behavior [10]

Normal results

Effective application of pain management techniques impairs or extirpates acute or chronic pain. This treatment can develop an individual’s quality of life and aid in recovery from injury and disease.

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